Re: [PSES] 62368-1 Section 6.4.8 Flammability Confusion

[John Woodgate]

Can you please share the format of your 'document and worded' exercise? 
I might be able to get at lease a small part of IEC interested in it.

Best wishes John Woodgate OOO-Own Opinions Only www.woodjohn.uk 
Rayleigh, Essex UK MAY THE VIRUS NOT BE WITH YOU
On 2020-05-06 20:40, John E Allen wrote:

IMHO & TBH. I encountered such inconsistencies in IEC standards too 
many times – which was why I “dissected” several standards (notably 
60950, 60204 and 61010-1), rigourously followed the various 
cross-references, and then documented and worded them in a form that 
would allow your (“average” in safety compliance issues but otherwise 
very competent!) development engineers to understand and then meet the 
 requirements of the standards in question.

Great pity that the IEC tech committees /never /seem to do the thing - 
but, if they did then their standards and Technical Report formats 
would be far more easily and clearly understood by /_everyone_/_!_

__

John E Allen

W.London, UK.

*From:*John Woodgate <j...@woodjohn.uk>
*Sent:* 06 May 2020 19:45
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* Re: [PSES] 62368-1 Section 6.4.8 Flammability Confusion

This is the sort of thing that can easily happen in a huge document. 
It is extremely difficult, especially where there is a chain of 
forward and back cross references, and text pushed off from its 
primary context to multiple annexes, to ensure internal consistency.

Best wishes John Woodgate OOO-Own Opinions Only www.woodjohn.uk 
<http://www.woodjohn.uk> Rayleigh, Essex UK MAY THE VIRUS NOT BE WITH YOU

On 2020-05-06 18:35, Carl Newton wrote:

    I'm wondering if any list members can explain the rationale behind
    62368-1,  in sections 6.4.8.2.2 and 6.8.8.4.  I'm looking at the
    2014 edition.

    Clause 6.4.6,  Control of fire spread in a PS3 circuit, states
    that, "/Fire spread in PS3 circuits shall be controlled by
    applying all of the following supplementary safeguards/:".  In
    that clause it includes, "/by providing a fire enclosure as
    specified in 6.4.8./"

    Clause 6.4.8.2.2, /Requirements for a fire enclosure/, states
    "/For circuits where the available power does not exceed 4 000 W
    (see 6.4.1), a fire enclosure shall comply with the requirements
    of Clause S.1./"  That clause then goes on to say that V-1 is
    acceptable....

    Clause (6.4.8.4) is addressing "Separation of a PIS from a fire
    enclosure and a fire barrier" and is only requiring the
    application of the S.2 flame test, which I believe is less
    demanding in that only a 60 s flame is applied rather than three
    steps up to 120 s for the S.1 test method.  Clause 6.4.8.4 then
    goes on to state that a V-0 material is excluded from the
    requirement.  So unless I'm mistaken, this clause 6.4.8.4 (which
    addresses separation) is requiring a lesser flame requirement than
    S.1, yet goes on to exclude V-0, but not V-1.

    I don't see the rationale.  I must be missing something here. The
    most fundamental question in my mind here is why does 6.8.8.4
    allow the S.2 test method?

    Thanks,

    Carl

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